An intense electromagnetic pulse (EMP) of short duration produces a strong electromagnetic field surrounding the pulse source. A particularly strong electromagnetic field can produce transient voltages on unprotected or poorly protected electrical conductors. Such an occurrence is likely to permanently damage electrical devices or cause them to malfunction either temporarily or permanently. Any device containing metal oxide semiconductors, such as computers and telecommunications equipment, is particularly susceptible to damage from an electromagnetic pulse. Accordingly, a device generating an EMP pulse can be used to intentionally disable electronic equipment. This can have military applications, but may also have other applications, particularly when implemented on a small, controlled scale.
An EMP device can be fabricated by filling a metal cylinder with an explosive material. A conductive coil is formed around, but slightly apart from, the cylinder. A current is applied to the coil to create a magnetic field. The explosive material is then ignited at one end and explodes, thereby expanding the cylinder. The explosion continues to expand the cylinder as it moves along the cylinder length. As the cylinder expands, it contacts the coil creating a traveling short circuit. The magnetic field is compressed by the short circuit, and energy from the explosive is transferred to the magnetic field, causing an increasing current pulse. This design can create electromagnetic radiation of sufficient strength to damage electrical devices.
EMP devices, such as described above, will create radiation having frequencies on the order of one MHz or less. Radiation at these frequencies is typically emitted in all directions and cannot be focused on a specific target. In addition, the explosion required to initiate the electromagnetic pulse can cause significant damage. These effects make the damage caused by the device difficult to control. Additionally, the EMP pulse may damage the device itself before it is fully detonated. Therefore, a need exists for an EMP device capable of producing radiation that does not require explosive material, that is not susceptible to premature destruction and that can produce radiation which can be directionally controlled.